A touch panel that detects that a finger, a stylus, or the like of a user has come into contact with or approached a detection surface is known. In recent years, electronic devices in which touch panel functions (also referred to as touch sensor functions) that can freely perform various functions just by having a stylus or the like touch the display screen are provided in a liquid crystal display element such as a liquid crystal display screen are starting to become widely used. Such a touch panel is formed onto a display panel, and by displaying various types of buttons on the display screen as images, it is possible to realize data input substituting these displayed buttons for normal buttons. Thus, when applying such a touch panel to a miniature mobile device, it is possible to have the display and buttons share a common space, thus presenting great advantages such as being able to increase the size of the display screen, decreasing the amount of space dedicated to control parts, or reducing the number of parts.
Additionally, a technique is known in which a touch panel shares some of the structure of the display part. For example, a configuration is known in which pixel electrodes or an opposite electrode for liquid crystal display, or the source bus lines double as one of the detection electrodes (detection lines) of a capacitance detection type touch panel. If the configuration is shared in this manner, it is also possible to attain the advantage that the device can be made thin.
However, if the detection electrode doubles as an electrode for display in this manner, the display driving frequency and the detection driving frequency match due to functional reasons. As a result, even if an attempt is made to raise the detection driving frequency because the detection speed is low and the responsiveness to data input is bad, there is a problem that it is not possible to freely change the detection driving frequency due to restrictions in the display driving frequency.
Patent Document 1 discloses a contact detection device in which the detection speed is improved without raising the detection driving frequency. As shown in FIG. 19, in Patent Document 1, the touch panel 110 has a contact response part that includes driver electrodes E1 and detection electrodes E2, which respond to contact and cause an electrical change, and a contact driver scanning part 111. The contact driver scanning part 111 scans a detection surface 113A in one direction by applying drive voltage to the driver electrodes E1, and controls output of the electric change from the detection electrodes E2 in chronological order. At this time, the contact driver scanning part 111 performs a plurality of scans (Re1 and Re2) in parallel for a drive signal source S and a reversed drive signal source Sx for different regions in the touch panel 110. With this configuration, the detection speed is improved without raising the frequency for contact detection.
Also, as shown in FIG. 20, in Patent Document 1, the contact driver scanning part performs parallel scanning to two different regions in the contact response part and supplies drive voltages having phases that are 180° apart in phase with respect to each other to the two regions, the contact driver scanning part controlling the output of electric change in chronological order by performing scanning in one direction on the detection surface by applying drive voltages to the contact response part, which causes electrical change in response to an object to be detected coming into contact or approaching the detection surface.